The day 40 days before Good Friday in the Catholic/Christian Calendar. Marks the beginning of Lent.

In the Liturgical year, the first day of Lent. The Jewish and Christian scriptures mention prayer and repentence while fasting and being covered in ash and sackcloth; so, the Catholics started marking the beginning of Lent by putting ash on their foreheads. It's a tradition that extends back about 1,000 years. The ashes are made from the burnt palm branches used on Palm Sunday of the previous year.
Although it's not a holiday of obligation, Catholics flock to mass on Ash Wednesday to get their ashes and begin lent. Although many prayers are now used when the ashes are being administered, the old-time prayer everyone knows is:

Remember Man that you are Dust
And unto Dust you shall return.

ash wednesday is a catholic holiday that reminds catholics that they started out as ashes and will eventually become ashes again (in death). It is also a time of repentance of sin. During ash wednesday catholics attend mass (church) and the preist puts on teir forehead, a cross of ashes . the ashes come from the palms burnt from palm sunday of that year.

is the day Lent begins. It occurs forty days before Good Friday.

A religious day in Catholicism in which ash is placed on the foreheads to symbolize that we were made from ash and to ash we will become.

In Christian tradition, the first day of the 40-day season of Lent, which recalls the last days spent on earth by Jesus.

the day at the beginning of lent, which lasts 40 days for roman catholics and a fasting day, the day after fat tuesday.